Machines, often referred to as "chipper-shredders," have been in wide use for years for comminuting lawn and yard refuse. Owners of residential and commercial property use such machines to mulch grass clippings, small twigs and branches, leaves and the like. In the past, it had been common practice to place the comminuted refuse into bags and dispose of the bags and refuse in a landfill.
More recently, municipalities are becoming more concerned about the cost of procuring landfill space. A growing number of such municipalities prohibit many types of lawn refuse from being placed into a landfill. Consequently, chipper-shredder machines are increasing in importance since they reduce lawn refuse to small particle and "piece" sizes entirely suitable for use as garden, lawn and tree mulch. Chipper-shredder machines play an important part in returning valuable natural organic material, pulverized lawn refuse, to the soil.
There are number of manufacturers of such chipper-shredder machines and the patent literature illustrates several different machine configurations. Examples of such machines are shown in U.S. Pat. Nos. 5,156,345 (Baker); 5,102,056 (Ober); 5,018,672 (Peck); 4,875,630 (Carlson); 4,824,034 (Baker); 4,544,104 (Carlsson); 3,817,462 (Hamlin); 3,712,353 (Ferry) and others. While such machines have been generally satisfactory for their intended purpose, they are characterized by certain disadvantages.
For example, some models of chipper-shredders are driven by an electric motor, the torque-speed curve of which differs quite dramatically from that of a gasoline engine. And for chipper-shredders used by homeowners for residential applications, the machine must operate from a 15 A, 120 volt, single phase circuit. The fan and comminuting assembly of an electrically-powered machine is sized to be compatible with the motor. And when such assembly is steel--as is the case with known machines--the assembly diameter and mass are reduced for electric motor drive.
The resulting disadvantage is that the linear velocity and inertial energy of the comminuting knives decreases. The machine simply does not perform as well. And will a fan and comminuting assembly of decreased diameter, air flow rate is decreased.
Another disadvantage of known machines is that when they clog (as they will if abused by the user and sometimes do in any event), they are very difficult to unclog. Sometimes the user is required to (or believes he is required to) insert a tool of some sort into the fan and/or chipping chamber to try to get the fan and comminuting assembly to turn freely again.
Yet another disadvantage involves the fact that the designers of such machines have not fully appreciated the damage to the machine that might occur if internal parts break, e.g., if a knife flies off of the rotor or if the rotor breaks up. Nor have they appreciated how to minimize damage (and particularly damage to the prime mover) in the event of such a failure.
Another disadvantage is that designers of prior art machines have not yet fully appreciated the advantages of maximizing air flow out of the machine. High air flow helps "throw" chipped debris into a bag or the like and helps prevent clogging.
A chipper-shredder with enhanced user features addressing the above and other disadvantages would be an important advance in the art.